Powder Post Beetles

Powder post beetles were so named because the wood upon which they feed is generally eaten into a fine powder substance that looks just like a very fine saw dust. Powder post beetle infestation starts when building lumber has been improperly stored in yards or at building sites. While the lumber was being stored, they make their way into the wood and breed.

Adults beetles lay their eggs in the crevices of uncoated wood and even under the bark areas of the trunk. When the larvae hatch, they start their destructive feeding by meandering tunnels throughout the wood. Sometimes you can see the outline of tunnels near the wood's surface, following the soft areas of the grain, but in many cases you can't see any evidence at all that larvae are present. As the larvae bore, the tunnels behind them become packed with sawdust. They will stop near the surface of the wood, where they will mature. Usually in June, adults break will through the surface, leaving tiny round holes (the size of a pin) where they emerge. Others will leave bigger holes (the size of pencil lead). A fine powder like sawdust will spill from the holes, and can continue to spill out for some time even though an infestation is over. Normally, Powder Post Beetles have a 1-year life cycle; this means that the adults will appear only once each year. And because of this habit the larvae have a feeding period of many months.




As I stated earlier, where excess moisture is a problem, all efforts to correct the cause should be undertaken. It does, however, take wood a long time to dry out, and reducing moisture may not be enough to completely control powder post beetle infestations. The sooner these insects are controlled, the better. Delay only makes the damage greater.

If you find that you definitely have extensive Powder Post Beetle activity which is ruining your structure, there are several chemicals that can be used, but they will not penetrate sealed wood. A more extreme (and expensive) measure is to tent the house and use poison gas to eradicate the beetles. Once this is completed, a Carpenter must replace or reinforce any damaged structural members. Always ask a professional exterminator for advice about your specific situation before you go into extremes. In some cases you'll find it's nothing to be overly concerned about. When I find minor Powder Post Beetle damage that doesn't require replacing wood members, I usually inform my clients to simply monitor for further development.

If your house sits on a crawl space, or has a dirt basement, I recommend covering the earth with 4-6 mil. polyethylene sheeting to reduce the moisture in this area. Then monitor the surface of the sheeting for sawdust falling from the floor joists above.

Inspect the floor or moldings beneath interior wood walls. Little piles of sawdust indicate beetles have been in the wood, but are not necessarily a sign of active infestation.

Schedule annual inspections with a qualified licensed pest inspector.


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Last updated on  Dec 28, 2012